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linux/crypto/algboss.c
Eric Biggers 77251e41f8 crypto: algboss - don't wait during notifier callback
When a crypto template needs to be instantiated, CRYPTO_MSG_ALG_REQUEST
is sent to crypto_chain.  cryptomgr_schedule_probe() handles this by
starting a thread to instantiate the template, then waiting for this
thread to complete via crypto_larval::completion.

This can deadlock because instantiating the template may require loading
modules, and this (apparently depending on userspace) may need to wait
for the crc-t10dif module (lib/crc-t10dif.c) to be loaded.  But
crc-t10dif's module_init function uses crypto_register_notifier() and
therefore takes crypto_chain.rwsem for write.  That can't proceed until
the notifier callback has finished, as it holds this semaphore for read.

Fix this by removing the wait on crypto_larval::completion from within
cryptomgr_schedule_probe().  It's actually unnecessary because
crypto_alg_mod_lookup() calls crypto_larval_wait() itself after sending
CRYPTO_MSG_ALG_REQUEST.

This only actually became a problem in v4.20 due to commit b76377543b
("crc-t10dif: Pick better transform if one becomes available"), but the
unnecessary wait was much older.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=207159
Reported-by: Mike Gerow <gerow@google.com>
Fixes: 398710379f ("crypto: algapi - Move larval completion into algboss")
Cc: <stable@vger.kernel.org> # v3.6+
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reported-by: Kai Lüke <kai@kinvolk.io>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2020-06-15 17:38:54 +10:00

293 lines
5.9 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Create default crypto algorithm instances.
*
* Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
*/
#include <crypto/internal/aead.h>
#include <linux/completion.h>
#include <linux/ctype.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/rtnetlink.h>
#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/string.h>
#include "internal.h"
struct cryptomgr_param {
struct rtattr *tb[CRYPTO_MAX_ATTRS + 2];
struct {
struct rtattr attr;
struct crypto_attr_type data;
} type;
union {
struct rtattr attr;
struct {
struct rtattr attr;
struct crypto_attr_alg data;
} alg;
struct {
struct rtattr attr;
struct crypto_attr_u32 data;
} nu32;
} attrs[CRYPTO_MAX_ATTRS];
char template[CRYPTO_MAX_ALG_NAME];
struct crypto_larval *larval;
u32 otype;
u32 omask;
};
struct crypto_test_param {
char driver[CRYPTO_MAX_ALG_NAME];
char alg[CRYPTO_MAX_ALG_NAME];
u32 type;
};
static int cryptomgr_probe(void *data)
{
struct cryptomgr_param *param = data;
struct crypto_template *tmpl;
int err;
tmpl = crypto_lookup_template(param->template);
if (!tmpl)
goto out;
do {
err = tmpl->create(tmpl, param->tb);
} while (err == -EAGAIN && !signal_pending(current));
crypto_tmpl_put(tmpl);
out:
complete_all(&param->larval->completion);
crypto_alg_put(&param->larval->alg);
kfree(param);
module_put_and_exit(0);
}
static int cryptomgr_schedule_probe(struct crypto_larval *larval)
{
struct task_struct *thread;
struct cryptomgr_param *param;
const char *name = larval->alg.cra_name;
const char *p;
unsigned int len;
int i;
if (!try_module_get(THIS_MODULE))
goto err;
param = kzalloc(sizeof(*param), GFP_KERNEL);
if (!param)
goto err_put_module;
for (p = name; isalnum(*p) || *p == '-' || *p == '_'; p++)
;
len = p - name;
if (!len || *p != '(')
goto err_free_param;
memcpy(param->template, name, len);
i = 0;
for (;;) {
int notnum = 0;
name = ++p;
for (; isalnum(*p) || *p == '-' || *p == '_'; p++)
notnum |= !isdigit(*p);
if (*p == '(') {
int recursion = 0;
for (;;) {
if (!*++p)
goto err_free_param;
if (*p == '(')
recursion++;
else if (*p == ')' && !recursion--)
break;
}
notnum = 1;
p++;
}
len = p - name;
if (!len)
goto err_free_param;
if (notnum) {
param->attrs[i].alg.attr.rta_len =
sizeof(param->attrs[i].alg);
param->attrs[i].alg.attr.rta_type = CRYPTOA_ALG;
memcpy(param->attrs[i].alg.data.name, name, len);
} else {
param->attrs[i].nu32.attr.rta_len =
sizeof(param->attrs[i].nu32);
param->attrs[i].nu32.attr.rta_type = CRYPTOA_U32;
param->attrs[i].nu32.data.num =
simple_strtol(name, NULL, 0);
}
param->tb[i + 1] = &param->attrs[i].attr;
i++;
if (i >= CRYPTO_MAX_ATTRS)
goto err_free_param;
if (*p == ')')
break;
if (*p != ',')
goto err_free_param;
}
if (!i)
goto err_free_param;
param->tb[i + 1] = NULL;
param->type.attr.rta_len = sizeof(param->type);
param->type.attr.rta_type = CRYPTOA_TYPE;
param->type.data.type = larval->alg.cra_flags & ~CRYPTO_ALG_TESTED;
param->type.data.mask = larval->mask & ~CRYPTO_ALG_TESTED;
param->tb[0] = &param->type.attr;
param->otype = larval->alg.cra_flags;
param->omask = larval->mask;
crypto_alg_get(&larval->alg);
param->larval = larval;
thread = kthread_run(cryptomgr_probe, param, "cryptomgr_probe");
if (IS_ERR(thread))
goto err_put_larval;
return NOTIFY_STOP;
err_put_larval:
crypto_alg_put(&larval->alg);
err_free_param:
kfree(param);
err_put_module:
module_put(THIS_MODULE);
err:
return NOTIFY_OK;
}
static int cryptomgr_test(void *data)
{
struct crypto_test_param *param = data;
u32 type = param->type;
int err = 0;
#ifdef CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
goto skiptest;
#endif
if (type & CRYPTO_ALG_TESTED)
goto skiptest;
err = alg_test(param->driver, param->alg, type, CRYPTO_ALG_TESTED);
skiptest:
crypto_alg_tested(param->driver, err);
kfree(param);
module_put_and_exit(0);
}
static int cryptomgr_schedule_test(struct crypto_alg *alg)
{
struct task_struct *thread;
struct crypto_test_param *param;
u32 type;
if (!try_module_get(THIS_MODULE))
goto err;
param = kzalloc(sizeof(*param), GFP_KERNEL);
if (!param)
goto err_put_module;
memcpy(param->driver, alg->cra_driver_name, sizeof(param->driver));
memcpy(param->alg, alg->cra_name, sizeof(param->alg));
type = alg->cra_flags;
/* Do not test internal algorithms. */
if (type & CRYPTO_ALG_INTERNAL)
type |= CRYPTO_ALG_TESTED;
param->type = type;
thread = kthread_run(cryptomgr_test, param, "cryptomgr_test");
if (IS_ERR(thread))
goto err_free_param;
return NOTIFY_STOP;
err_free_param:
kfree(param);
err_put_module:
module_put(THIS_MODULE);
err:
return NOTIFY_OK;
}
static int cryptomgr_notify(struct notifier_block *this, unsigned long msg,
void *data)
{
switch (msg) {
case CRYPTO_MSG_ALG_REQUEST:
return cryptomgr_schedule_probe(data);
case CRYPTO_MSG_ALG_REGISTER:
return cryptomgr_schedule_test(data);
case CRYPTO_MSG_ALG_LOADED:
break;
}
return NOTIFY_DONE;
}
static struct notifier_block cryptomgr_notifier = {
.notifier_call = cryptomgr_notify,
};
static int __init cryptomgr_init(void)
{
return crypto_register_notifier(&cryptomgr_notifier);
}
static void __exit cryptomgr_exit(void)
{
int err = crypto_unregister_notifier(&cryptomgr_notifier);
BUG_ON(err);
}
/*
* This is arch_initcall() so that the crypto self-tests are run on algorithms
* registered early by subsys_initcall(). subsys_initcall() is needed for
* generic implementations so that they're available for comparison tests when
* other implementations are registered later by module_init().
*/
arch_initcall(cryptomgr_init);
module_exit(cryptomgr_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Crypto Algorithm Manager");